This program project consists of five experimental projects: 1) the development of an animal model for the carcinogenesis of inhaled benzene will be attempted by treating rats and mice to various exposure regimes of benzene vapor and by combining exposure of benzene with known leukemogenic agents; 2) the development of an animal model for the carcinogenesis of inhaled arsenic compounds will be attempted by exposing rats to a combination of arsenic trioxide aerosol and sulfur dioxide and by intratracheally instilling the components of Bordeaux mixture into rats; 3) the effect of fiber length on asbestos carcinogenicity will be studied by exposing rats to two different lengths of asbestos fibers which have the same aerodynamic mass median diameters. The development of lung damage will be monitored in vivo during the course of the exposures: 4) the interaction of atmospheres of HCl plus HCHO with DNA will be studied by measuring DNA damage by means of the S-1 nuclease assay in skin and nasal epidermal cells, as well as bacteria; and, 5) the amount of BCME and other alkylating agents in known, tumorigenic atmospheres of HCl plus HCHO will be determined by gas chromatographic and mass spectrometric techniques.